Until she declares otherwise, the assumption will be that she remains interested at least in exploring a presidential campaign for 2012. But after announcing that she intends to resign as governor of Alaska, that future comes with bigger question marks than ever.

The former vice presidential nominee's judgment and political instincts were called into question again by her decision to quit. Many Republicans believed she might not seek re-election to free herself up for a national campaign. But stepping away with almost 18 months left in her first term was beyond almost anyone's expectation.

Other prospective presidential candidates have decided to leave office. Mitt Romney chose not to run for a second term in Massachusetts when he decided to seek the presidency in 2008. Minnesota Gov. Tim Pawlenty already has announced that he will not run for another term next year and is seen as a likely candidate for the 2012 GOP nomination.

Neither Romney nor Pawlenty quit, as Palin did, midstream. And Palin's explanation for stepping down was even more inexplicable. She described the abandonment of her duties almost in noble terms, saying that by leaving now she would avoid the temptation that she ascribed to others who have not run again.

"I thought about, well, how much fun some governors have as lame ducks," she said. "They maybe travel around their state, travel to other states, maybe take their overseas international trade missions. So many politicians do that. And then I thought, that's what is wrong. … They hit the road, they draw a paycheck, they kind of milk it, and I'm not going to put Alaskans through that."

That is a fundamental misunderstanding of the responsibilities of governing. Every president becomes a lame duck in his second term. The same for governors, since many are term-limited. Do they "milk it," as Palin put it, or do most continue working hard to the end to finish off their terms with real accomplishments?

Palin need only look back at the GOP's favorite president for an answer. Some of Ronald Reagan's most significant foreign policy accomplishments came in the final two years of his presidency. Most politicians would find offensive her description of how they spend their final year or two in office.

Palin is entitled to resign the office. But in disparaging others to justify her course, she has left herself open to legitimate criticism that she is walking away for the wrong reasons.

"One of the worst things a politician can do is reinforce the rap against her," Whit Ayres, a Republican pollster, said Saturday in an e-mail message. "Resigning before her first term is up gives ammunition to all her critics."

Palin also cited the toll that life in the spotlight has taken on her and her family, and certainly it has been substantial. She talked about the relentless digging by political opponents and by the news media. She said she and her husband have accrued personal legal bills of half a million dollars from what she called frivolous ethics charges and "silly accusations." She said the state has spent millions on these investigations.

Virtually all those complaints have been dismissed. She agreed to repay the state about $10,000 for expenses involving trips with her children that were initially paid by the state. She was cleared of violating the law in the firing of Public Safety Commissioner Walter Monegan. But a special counsel found last October that she violated a state ethics law.

Palin hopes her resignation will bring all these investigations and questions to an end. But is fear of frivolous accusations justification for resigning? If she decides to run in 2012, her rivals will question why she walked away when things got uncomfortable.

It's possible Palin needs a timeout to reassess the future. Beyond energy policy, there is no issue with which she is associated. She has not used the months since the campaign ended to fill out her political profile. Beyond predictable criticism of President Barack Obama as a proponent of big government, she has not been part of the national debate.

Gary Bauer, the conservative chairman of the Campaign for Working Families, issued a statement Saturday saying reports of Palin's political death are exaggerated. "Sarah Palin is a force in the GOP and one of the most promising figures in American politics, whether she is governor of Alaska or not," he said. "A year from now, a lot of pundits may be eating their words."

Bauer is correct in asserting that Palin is a force within the party. What gives Palin a political future is that she has passionate supporters who form part of the Republican base. She has defied the odds throughout her career and might do so again.

Among social and religious conservatives, Palin will remain popular, though if she runs in 2012 she probably will have competition for those voters from former Arkansas Gov. Mike Huckabee and perhaps others.

More fundamental is the question of whether she can break out beyond that core of support. No Republican has won the nomination in the modern era if he or she has been strongly opposed by the religious and cultural conservative base. That base alone, however, has generally not been enough to win the nomination, although as the party shrinks, the influence of those voters grows. Other prospective candidates have greater capacity to attract a wider coalition.

Palin is bringing this chapter of her life to a conclusion that is consistent with her style. The next chapter, if it includes another bid for public office, will test the limits of that style and the substance behind it.